Nowadays, in a communication apparatus or an information processing apparatus such as a computer or the like, a signal processing device of the plug-in unit type in which electronic circuit units are coupled to a wiring unit (hereinafter, referred to as a back wiring board (BWB)) is used.
The BWB is electrically coupled to electronic circuit units and is configured to supply power to the electronic circuit units and to allow signals to be sent and received among the plurality of electronic circuit units.
Japanese Laid-open Patent Publication No. 2005-26306 discloses a housing structure describing assembly of a high-strength housing body using a smaller number of assembling steps and a smaller number of components in electronic equipment using a BWB of the type as mentioned above.
FIG. 6 is a related art schematic diagram illustrating an example of a signal processing device 300 which is electronic equipment using a BWB. The signal processing device 300 illustrated in FIG. 6 includes a BWB 302, electronic circuit units 306, 308, 310, a control unit 322 and a cross-connection unit 324.
The electronic circuit units 306, 308 and 310 respectively include main signal devices 306a, 308a and 310a that output signals and unit control sections 306b, 308b and 310b that control timings (output phases) at which the signals are output from the main signal devices 306a, 308a and 310a. 
The cross-connection unit 324 includes a cross-connection device 324a that performs cross-connection processing using the signals sent from the electronic circuit units 306, 308 and 310 and a unit control section 324b that controls the cross-connection processing.
The control unit 322 includes a device control section 322a. The device control section 322a generates a control signal, sends the generated control signal to the electronic circuit units 306, 308, 310 and the cross-connection unit 324 via a control bus disposed in the BWB 302 to control the operations of the electronic circuit units 306, 308 and 310 and the cross-connection unit 324.
The BWB 302 includes wirings through which the BWB 302 is coupled to the electronic circuit units 306, 308 and 310 and the cross-connection unit 324. The BWB 302 is coupled to the electronic circuit units 306, 308 and 310, the control unit 322 and the cross-connection unit 324 respectively via connectors 328, 330, 332, 334 and 336.
In the signal processing device 300 illustrated in FIG. 6, a plurality of wirings which are respectively coupled to the electronic circuit units 306, 308 and 310 are concentrated on and arranged in the connector 336 that serves to couple the cross-connection unit 324 to the BWB 302 and signals A, B and C are sent to the cross-connection unit 324 via the connector 336.